Homojunction Back Contacts Enable Efficient Cu 2 O Photocathodes
Jinshui Cheng, Linxiao Wu, Keming Li, Qiushuang Tian, Linrui Duan, Jia Zhao, Daniele Benetti, James R. Durrant, Jingshan LuoABSTRACT
Enhancing carrier separation and extraction is crucial to achieve efficient metal oxide photoelectrodes for photoelectrochemical (PEC) water splitting. Here, we report a highly efficient Cu 2 O photocathode based on p + /p back‐contact homojunction. The homojunction significantly enhances hole‐selective extraction while suppressing electron backflow at the back‐contact interface, leading to marked improvements in PEC performance. The optimized photocathode delivers a hydrogen evolution reaction (HER) onset potential of 1.1 V and a saturated photocurrent density of ∼8.0 mA cm −2 . Furthermore, the p + /p back homojunction design enables the fabrication of a semi‐transparent Cu 2 O photocathode, which, when integrated with a perovskite solar cell in a tandem configuration, achieves a solar‐to‐hydrogen (STH) efficiency of 7.31%. This work demonstrates a viable strategy for advancing metal oxide photoelectrodes via homojunction engineering.